1. Field of the Invention
The present invention relates in general to an on-board DSRC (Dedicated Short-Range Communication) apparatus for use in ETC (Electronic Toll Collection) systems or the like of ITS (Intelligent Transport Systems), and more particularly to an on-board DSRC apparatus in which the degradation of the antenna characteristics due to the change in the peripheral state of an antenna is prevented.
2. Description of the Related Art
In general, in an on-board DSRC apparatus (hereinafter, it is also referred to as xe2x80x9can on-board apparatus xe2x80x9d for short, when applicable), an antenna for transmission and reception of an electric wave is installed (placed or embedded) in the vicinity of a front glass part and a dash-board in order to communicate effectively with the associated one of antenna of on-road communication machines for charge collection.
FIG. 5 is a side view showing the installation state of a conventional on-board DSRC apparatus, and FIG. 6 is a front view of the conventional on-board apparatus when viewed from the inside of a vehicle. In these figures, there is shown the case of the on-board apparatus which is installed after having purchased the vehicle.
In FIGS. 5 and 6, an on-board apparatus 1 is installed on a dash-board 2 and also firmly fixed thereto in such a way as to be readily viewed by a driver.
A front glass part 3 of the vehicle is provided over the dash-board 2 and also the front face of the dash-board 2 is provided with a steering wheel 4, a speed meter 5 and the like.
An antenna and a control unit (both not shown) are provided in the inside of the on-board apparatus 1 in order to communicate with the associated one of on-road communication machines for charge collection (not shown) which is installed on the travelling road of the vehicle.
The antenna is provided on the upper side of the on-board apparatus 1 and has the directivity towards an antenna of the associated one of the on-road communication machines for charge collection (located above the road).
While the on-board apparatus 1, as shown in FIGS. 5 and 6, may be purchased in a shop for selling products for vehicles to be installed on the dash-board 2, a vehicle may be sometimes equipped with the on-board apparatus in accordance with the standards when having sold the vehicle, or otherwise the on-board apparatus 1 may be embedded in the dash-board 2 as a result of purchasing an option.
In the on-board apparatus 1 constructed as described above, its antenna characteristics (relating to the reflection of an electric wave, the speed and the like) are changed in dependence on a dielectric constant and a thickness of an object (the front glass part 3 or the like) which is present in front of the antenna, and a distance between the antenna and the object which is present in front of the antenna.
Therefore, there is the possibility that the performance of the antenna characteristics (the resonance frequency, the polarized wave characteristics, the antenna gain and the like) may be degraded due to the influence of the object which is present in front of the antenna.
In particular, in such an on-board apparatus 1, since the antenna for the circularly polarized wave is employed and also the characteristics are easy to be degraded due to a dielectric constant and a thickness of an object which is present in front of the antenna, it is impossible to disregard. the change in the peripheral state of the on-board apparatus 1.
In addition, in the case where the antenna of the on-board apparatus 1 is already embedded in the dash-board 2 when purchasing a vehicle, since it is difficult for a driver to recognize the position of the antenna, a baggage is easy to be unpreparedly placed on the on-board apparatus 1. As a result, the situation in which the desired antenna characteristics may not be obtained is easy to occur.
As described above, in the conventional on-board DSRC apparatus, there arises the problem that in the case where a driver installs the on-board DSRC apparatus on the dash-board, the characteristics of the antenna (the resonance frequency characteristics, the polarized wave characteristics, the antenna gain and the like) may be degraded due to a distance between the antenna and an object (the front glass part) which is present in front of the antenna and a dielectric constant, so that the desired antenna characteristics are not obtained.
In addition, in the case where a driver places unpreparedly a baggage on the upper part of the antenna, there arises the problem that the desired antenna characteristics may not be obtained due to a dielectric constant and a thickness of the object (the baggage) placed on the upper part of the antenna.
In the light of the foregoing, the present invention has been made in order to solve the above-mentioned problems associated with the prior art, and it is therefore an object of the present invention to provide an on-board DSRC apparatus in which the degradation of the antenna characteristics is prevented by adopting the construction in which it is difficult for any of objects to lie between an antenna of the on-board apparatus and a front glass part of a vehicle.
According to one aspect of the present invention, there is provided an on-board DSRC apparatus including an antenna and a control unit for communicating with the associated one of on-road communication machines which is installed on a travelling road of a vehicle and being installed in the vicinity of a dash-board of a vehicle, wherein positioning means is provided between the antenna and a front glass part of a vehicle so that a distance between the antenna and the front glass part o:f the vehicle is set to a fixed value.
According to another aspect of the present invention, there is provided an on-board DSRC apparatus wherein the positioning means is comprised of a dielectric part having a predetermined dielectric constant so that the antenna characteristics are ensured to predetermined values.
In addition, according to still another aspect of the present invention, there is provided an on-board DSRC apparatus wherein the matching is obtained for the antenna of the on-board DSRC apparatus by taking a thickness and a dielectric constant of the dielectric part into consideration.
In addition, according to yet another aspect of the present invention, there is provided an on-board DSRC apparatus wherein the positioning means is projectingly provided in the on-board DSRC apparatus in such a way as to be located in the vicinity of the peripheral part of the antenna.
In addition, according to a further aspect of the present invention, there is provided an on-board DSRC apparatus wherein the antenna is installed on the dash-board of the vehicle and the positioning means is provided up to the position which reaches the front glass part of the vehicle.
Also, according to an even further aspect of the present invention, there is provided an on-board DSRC apparatus wherein the positioning means has a printing display part on the surface facing a driver of the vehicle.
Also, according to another aspect of the present invention, there is provided an on-board DSRC apparatus wherein the on-board DSRC apparatus is installed in such a way as to be adhered closely to an inner wall of the front glass part of the vehicle.
Also, according to still another aspect of the present invention, there is provided an on-board DSRC apparatus wherein the control unit transmits and receives information relating to the charge collection to and from the associated one of the on-road communication machines for charge collection to carry out automatically the charge collection on the basis of the information relating to the charge collection.
In addition, according to yet another aspect of the present invention, there is provided an on-board DSRC apparatus including an antenna and a control unit for communicating with the associated one of on-road communication machines which is installed on a travelling road of a vehicle and being installed in the vicinity of a dash-board of a vehicle, wherein the antenna is embedded in the dash-board, and the dash-board has a projecting member on a upper face corresponding to the position where the antenna is embedded.
In addition, according to a further aspect of the present invention, there is provided an on-board DSRC apparatus wherein the projecting member is provided in the position corresponding to the peripheral part of the antenna.
In addition, according to an even further aspect of the present invention, there is provided an on-board DSRC apparatus wherein the projecting member has a printing display unit on the surface facing a driver of the vehicle.
Also, according to another, aspect of the present invention, there is provided an on-board DSRC apparatus wherein the control unit transmits and receives information relating to the charge collection to and from the associated one of the on-road communication machine s for charge collection to carry out automatically the charge collection on the basis of the information relating to the charge collection.
Also, according to still another aspect of the present invention, there is provided an on-board DSRC apparatus including an antenna and a control unit for communicating with the associated on e of on-road communication machines which is installed on a travelling road of a vehicle and being installed in the vicinity of a dash-board of a vehicle, wherein the antenna is embedded in the dash-board, and the dash-board has a printing display unit on a upper face corresponding to the position where the antenna is embedded.
Also, according to yet another aspect of the present invention, there is provided an on-board DSRC apparatus wherein the control unit transmits and receives information relating to the charge collection to and from the associated one of the on-road communication machines for charge collection to carry out automatically the charge collection on the basis of the information relating to the charge collection.